Manufacture of trinitrotoluene



Patented Aug. 14, 1945 MANUFACTURE oF TRINITROTOLUENE Francis .Stapleton Chambers, Jr., Woodbury, N. J., and Clifford Akeley Woodbury, Media, Pa.,' assignors to E. I. du Pont de Nemours &

CompanmfWilmington, Del., a corporation of a l Delaware :[No Drawing. Application-March 27,1943, a ,Serial No. 480,836 1 3 Claims.

This invention relatesto improvements in the manufacture of trinitrotoluene, and more particularly to the removal of acidity from the crude acid-retaining material. I

The manufacture of trinitrotoluenefrom toluene is conventionally carried out in three, stages, wherein mono-, di-, andtrinitrotoluene are obtained in successive .,nitrations using predetermined temperatures and compositions of nitration acids. Only the trinitrocompound requires careful purification since the others are intermediate products in itspreparation, Trinitrotoluene is present in the final stage insuspension and. partial solution in the: spent-acid, comprising a blend of sulfuria mtric, and nitrosyl sulfuric acids along with dissolved nitrobodies. Since the trinitration temperature is above the freezing point of trinitrotoluene, this latter material will be in molten form. After a short period of standing there is a-definite line of separation between themolten trinitrotoluene and the spent acid, and this latter can be drawn ofi.

' The molten trinitrotoluene which has been separated from the spent acid retains a certain amount of included acid as well as other impurities. customarily this molten material is washed repeatedly with successive quantities of hot water and agitatedw during the washing with intermediate separations of the wash waters. These wash waters are discarded; Because of the relatively high solubility of the trinitrotoluene in hot water, such treatments lower the yield of purified material andat the same time introduce the problem of recovering the dissolved trinitrotoluene from the discarded wash waters. In spite of; this loss, this treatment hasibeen considered; necessary be: fore in the purification of trinitrotoluene.

It is an object of the present invention to eliminate the necessity for recovering trinitrotoluene conventionally lost during hot water washes and render unnecessary the catch boxes and other apparatus required for. such recovery. A further ob ject is an improved process for obtaining a substantially pure trinitrotoluene product from the separated crude material containing retained acid and. other impurities. -'An additional object is the removal of acidity. fromzcrude'trinitrotoluene. A further object is an improved process for refining trinitrotoluene. Additional objects will be discerned from the following description of the invention:

We have found that the foregoing objects are accomplished and the disadvantages of the prior art methods overcome by separating the molten, newly formed crude trinitrotoluene from the bulk of the spent acid, adding' thereto cooling water having a temperature below the solidification point of the molten crude, to crystallize the latter, and neutralizing by the addition of an alkali such as sodium carbonate. The alkali can be added to the trinitrotoluene either before orafter the solidification has occurred. Alternatively, the trinitrotoluene may be crystallized in the presence of the alkali, by adding alkali to the cold water employed to cool and crystallize thetrinitrotoluene. The removal of acidity may be effected by any of the foregoing'treatments. a

After the acidity hasibeen removed, the crude neutralized trinitrotoluene may be used as such, or if desired, a purified product may be obtained by further treatment. i l I Inthe event that a purified product is required, the solid particles of neutralized trinitrotoluene preferably are subjected to a surface treatment with a solution of sodium sulfite or other watersolubleinorganic sulfite, preferably a sulfite of an alkali metal. I I

The following examples will serve as more specific embodimentsof the application of our invenand not as limiting in any way.

tion and are set forth by way of illustration only Example 1v Following the completion of nitration of dinitrotoluene to trinitrotoluene, separation offthe latter material inmolten form from the bulkor a temperature of F. which were introduced gradually with agitation. Crystallization took place at around 160 F. Neutralization of. the acid solution by means of sodium carbonate followed, a total of approximately lbs. of sodium carbonate in solidform being added gradually, the end point being indicated by test papersand by a slight brown color' of the water. Following the neutralization, '180 gallons of a l6% so1uti0n of sodium sulfite were introduced-into the mixture for the purpose of washing isomeric and other impurities from the surface of the crystals. The slurry was then pumped to the filter and the crystals washed with large amounts of cold water. The trinitrotoluene obtained by the foregoing rocess, after suitable drying and granulation Was of good quality, having a freezing point of 80.43 C.

Y or waste bi et fI e ersbdium 2 Example 2 The procedure of Example 1 was carried out, with the variation that the neutralization with sodium carbonate was efiected while the acid-retaining trinitrotoluene was still in molten form.

, The same 'amount of cooling water was then added and crystallizationeffected. Surface treatment of the crystals with sodium sulfite solution was carried out and the crystals filtered and washedfi" Agitation .was used in the as in Example 1. various steps and the same quantitiesoi water;

sodium carbonate, and so.dium. sulfite .-solution'1 were employed. The productl iuas-ifof.excellenti purified =crysta1s were quality and good yields of obtained. 1

In the foregoing examples, the acidity was neutralized by means of alkali; inpnecase aiterm crystallization, and in the other while theutrin t trotoluene was in molten form. It should be understood that our invention includes also these es. oil-steps he e vt e;s 1 "atsl smqltsn e ii a i -r tainin ,triniirot ene i ctrs l zed. shy. e ad ti n 0 .c plins water, and. wha ia li t face acidit onthecrys a s u ra za on bu .byfilt tim enemas 11. h fi t by a u c s onpiwaterweshsstsuq acidree. .mate al an then; b nr s lu iedlaei pur fied. if des re y tre ment. wit a Water: o uble n rs n csul telhe ;l Qf.ir r9- toluene. usually exp r e ced... n. the imc ees s 19f;

acidity. he, gznplg ever, for. example pota um carbonate l t-h d iz m dium ,and thelilse 'm .1...

The crystals have been described as be ng given a surface washin gzmthan aqueous solution of sodium sulfite. Such a sulfite solution has the property of dissolving-the isomeric formsof the 2 4.56 etrinitroto'luene which are "present mairily -on the, surface of the c'rystafls it has little solvent power, however, for the 2 Adi-isomers It will understood-that place ofsediumsulfite we may employ any lather water soluble ino-rganic sulfite;

In fact sulfi-te treatment :of the crystals isnot an essential step in our invention, which. -comprises; the production of -a substantially pure trinitro toluene iproduct from the aci-dsretainingJn'ate-v rial separated =from-the b'ulkof 'the tri-Spent acid.

withoutthe necessity for using and -discarding:

hot wash waters;

The advantages ofleur inventionsnyill be 'appare.

ent when the resultanttsavings are understood.

themanufacture oftrinitrotoluene iande-its sub-. A

sequent purification according t0 the mathQdS lot the ,prior art, the treatment of, a;molten mate;,

,: substantially below s'aid solidifies.

-rial with a number of hot water washes entails considerable loss because of the solubility of trinitrotoluene in hot Water. Such Wash waters are commonly passed into so-called catch boxes,

where coolingis allowed to take place and the dissolved trinitrotoluene precipitates out. The installationlof such catchboxes and their upkeep and occasional replacement are a matter of considerable expense and interfere with smooth op- 10' .ithewashwaters, deterioration of such apparatus erating procedures. Because of the acidity of is more ,rapid than would otherwise be the case. 'Since eurinventionavoids the necessity of dis- 'c'a rding"ariy hot water washes and, in its preferr ed-embodiments, effects the neutralization of substantially all acidity, catch boxes may be eliminated and increased yields will result.

Ourinvention'has been described at length in theforegoing. It will be understood that many Variations in details of operations, amount and kinds of materials used, and succession of steps maybe employed =without departing' "from the spirit of the invention.- For instance, *it is some-- times desirable to 00 01 the slurry atter the intro duction of the alkaline sulfi te ahdbeiore filtering.- We intend be' lim ited only by t he following t t laim j. I}... .t :1 l. i- "Weclaim: 1."In' the manufacture of 'trin itretoluene and the preparation oi --a crystallined; substantially acid-free product; thesteps-Which comprise step-- arating the molten tr initrotoluene from the bulk of th'e spent-acid, co ti'tacting the acid-retairimg molten material taken directlyfro'm the sepa-' ration step Wi'thalkali and an; aqueous meclium,- cooling the" mixture below the solidification point of the-crude trinitroteluene,"and-discarding aqueous liquid at 'atemp'erature substantially below said solidification point I and--o nly at such termepera ture .i I....'Ll l l, J. l. 2.-In the-manufacture o'f trinitretoluene-and the 'preparatiompt a crystallized; substantially acid-free prodii'ctz' the steps which comprise separe/ting the molten trim treteluen rrem the bulk of- -thespent 1 acid, treating the *'-=acidretai-riin'g' molten material 7 taken directly trdiiithe' separat tio'n' step with Water and -'cool ing"{ the *mixture below the solidification point'oi the-crude"tririi trotoluene; neutralizing the mixture w-ith' 'sL-lkali; and discarding aqueous diquid- 'at -a temperature FP'OiIIt and onlyat such'temperatureuf ---3.- In--the manuta'cture ott "trdtoluene end-- theprep a-reition efa; crystalhized, A substantial-151 acid-free product: the' steps of --'se'parating "the molten "trinitrotolueneirem' the bulk of spent acid treating the amid-retaining mlten material taken directly i r'o'm the separation I step 1 waten coeling "the mixture solidification pom-t of the --c-r-ude trm itrdtoluene, separating the crystals ir-omthemieid-waterfiwaslhing i said separated crystals-'wifih suflidiemtwaterto remove the greater part iof the aeidity theretrom and. discarding aqueous liquid at awtemperaturelsuba stanti'ally below said solidification point we :only at such'temperature. w l a STABLETONICHAMBERS, slit.

*CLIFFGRD AKEIEYJWOODHURZL a 1,;

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